1. Field of the Invention
The present invention relates to an image projection apparatus, such as a liquid crystal projector, which allows insertion and extraction (attachment and detachment) of an optical element constituting part of an optical system.
2. Description of the Related Art
Image projection apparatuses such as liquid crystal projectors introduce high intensity light emitted from a light source to a light modulation element such as a liquid crystal panel through an optical system constituted by various optical elements, and introduce the light modulated by the light modulation element to a projection lens through the optical system to project the modulated light onto a projection surface.
The optical elements constituting the above-mentioned optical system include a plastic optical element whose durability to high intensity light is lower than those of optical elements made of inorganic materials such as glass and which thereby requires replacement thereof after a predetermined use time. Especially, light density is high around the light modulation element where the light from the light source is condensed, which may inevitably make it necessary to replace the plastic optical element such as a polarizing element disposed around the light modulation element.
For example, Japanese Patent Laid-Open No. 2003-215701 discloses a projector including a color separation/combination optical system that separates light from a light source into plural color lights to introduce the respective color lights to plural light modulation elements and combines the color lights modulated by the light modulation elements to introduce the combined color lights to a projection lens. This projector has a configuration that replaceably (insertably and extractably) holds a polarizing plate as an optical element constituting part of the color separation/combination optical system.
As disclosed in Japanese Patent Laid-Open No. 2003-215701, a direction in which the replaceable optical element constituting part of the conventional color separation/combination optical system is inserted thereinto and extracted therefrom is same as that in which a flexible wiring substrate is extended from the light modulation element, the flexible wiring substrate connecting the light modulation element with an electrical circuit substrate that drives the light modulation element. In this case, in order to insert and extract the optical element into and from the color separation/combination optical system, it is necessary to detach the flexible wiring substrate from the electrical circuit substrate or separate the electrical circuit substrate from the color separation/combination optical system.
However, such detachment of the flexible wiring substrate provided for the light modulation element from the electrical circuit substrate may require, when the flexible wiring substrate is again connected to the electrical circuit substrate after the replacement of the optical element, adjustment of a driving voltage of the light modulation element in consideration of individual differences of characteristics of light modulation elements. Moreover, static electricity existing on an assembler may generate unnecessary electric current flowing from the flexible wiring substrate to the light modulation element, which may cause a defective operation of the light modulation element. Furthermore, the detachment of the electrical circuit substrate is an extremely extensive work, which is undesirable.